STAMFORD­ -- In a sign of investor confidence in the city's rental apartment market, South End developer Building and Land Technology has sold The Lockworks, one of its large-scale apartment complexes in Harbor Point, for $130 million.

A Wafra representative did not immediately return a call seeking comment. The Manhattan company boasts real estate assets in the U.S. and Canada in excess of $1.4 billion.

The Lockworks, part of the Harbor Point development known as Yale & Towne, opened for leasing in October 2011. It was the third residential development to open in Harbor Point after The Lofts, a series of converted six-story factories on Henry Street that are also part of Yale & Towne, and 101 Park Place, a 15-story high-rise on Washington Boulevard. The fourth, a 22-story on Commons Park South, called The Infinity, opened last summer.

Rents at The Lockworks range from $1,815 a month for a studio to $3,450 for a three-bedroom unit.

Al Mirin, a senior director at Cushman & Wakefield, said the deal was not surprising in light of the market.

"The most popular investment is rental apartments," he said, adding that Lockworks was a brand-new development in an improving neighborhood. "For a long-term hold, if you're a seller, it's a good time to sell, and if you're a buyer, it's a good time to buy."

Although he said he was not privy to Lockwork's financial details, Mirin said sales of downtown rental buildings have typically offered buyers a return of between 5 percent to 6 percent.

Previous downtown sales, he said, have included buildings that fetched in the $100 million range.

Most recently, in 2011, developer Randy Salvatore sold a 94-unit apartment building he built on Washington Boulevard for $20 million.

It is not clear whether BLT intends to sell other pieces of Harbor Point, an estimated $3.5 billion redevelopment project that is roughly halfway finished.

With more than 1,350 units either completed or underway, BLT has sought approvals for two more apartment complexes at Yale & Towne. The Zoning Board is to vote on a five-story, 102-unit building and a six-story, 257-unit building, both on Market Street. All told, the plan for Harbor Point calls for construction of 4,000 housing units.

The developer is vying to win city approval for a controversial plan to build a $750 million office headquarters for Westport-based hedge fund Bridgewater Associates on a 14-acre South End peninsula. The site, which was formerly the home of Yacht Haven West Marina, is zoned for boatyards.